1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a method for manufacturing the same, and an electrophotographic apparatus having the electrophotographic photosensitive member.
2. Description of the Related Art
As one type of an electrophotographic photosensitive member (hereinafter referred to simply as “photosensitive member” as well) to be used in an electrophotographic apparatus, a photosensitive member is known which employs hydrogenated amorphous silicon as a photoconductive material (hereinafter referred to as “a-Si photosensitive member” as well).
The a-Si photosensitive member is manufactured by forming a photoconductive layer which is formed from the hydrogenated amorphous silicon on a conductive substrate (hereinafter referred to simply as “substrate” as well), generally, with a film-forming method such as a plasma CVD method.
Conventionally, it has been investigated to improve various characteristics such as electrical properties, optical properties, photoconductive properties, characteristics in a use environment, and the stability with time of the a-Si photosensitive member. As one of technologies for improving the characteristics of the a-Si photosensitive member, a technology is known which provides a surface layer formed from hydrogenated amorphous silicon carbide (hereinafter referred to as “a-SiC” as well) on a photoconductive layer that is formed from hydrogenated amorphous silicon (hereinafter referred to as “a-Si” as well).
In Japanese Patent Application Laid-Open No. 2002-236379, it is described to provide a region in which a ratio (C/(Si+C)) of the number of carbon atoms (C) with respect to the sum of the number of silicon atoms (Si) and the number of carbon atoms (C) gradually increases toward the surface side of the photosensitive member from the photoconductive layer side, (in the present invention, hereinafter referred to as “change region” as well), in the surface layer formed from the a-SiC, and to make this change region contain an atom which belongs to Group 13 of the Periodic Table (hereinafter referred to as “Group 13 atom” as well).
In recent years, the digitization and the full colorization of an electrophotographic apparatus are progressing, and the image quality of an output image becomes higher.
In the digitized and the full-colorizing electrophotographic apparatus, in order to enhance the image quality of the output image, negative electrification is adopted for electrifying the photosensitive member, an image area exposure method (IAE) is adopted for forming an electrostatic latent image, and a negative toner is adopted as a color toner, in many cases.
Accordingly, the photosensitive member to be negatively electrified is required to have a function of blocking an electric charge (electron) from being injected into the photoconductive layer from the surface of the photosensitive member as much as possible, in order to have the charging ability when the photosensitive member is negatively electrified.
Conventionally, it has been attempted in the a-Si photosensitive member to be negatively electrified to enhance the charging ability shown when the photosensitive member is negatively electrified, by providing a portion containing the Group 13 atom in the surface layer as a portion for blocking the electric charge from being injected into the photoconductive layer from the surface of the photosensitive member, as is described in Japanese Patent Application Laid-Open No. 2002-236379.
However, in recent years, the case has increased where a large amount of digitized information is output, and the requirement of outputting an image at high speed has accordingly increased. In order to output the image at high speed, it becomes necessary to further enhance the charging ability and the luminous sensitivity of the photosensitive member.
An object of the present invention is to provide an electrophotographic photosensitive member which is excellent in charging ability when the photosensitive member is negatively electrified and in luminous sensitivity, a method for manufacturing the same, and an electrophotographic apparatus having the electrophotographic photosensitive member.